Food supplementation is increasingly used as a conservation tool. However, little is known about how
much supplemental food is used by target populations or the degree to which the abundance of natural
food affects the utilization of supplemental food. Long-term supplementation programmes could cause
individuals to rely almost exclusively upon supplemental food and, consequently, lose some skills needed
to forage efficiently on natural food. This may result in reduced fitness upon discontinuation of supplemental
food. The Iberian lynx (Lynx pardinus) preys almost exclusively upon European wild rabbits (Oryctolagus
cuniculus), and some populations are thought to be food limited. We quantified the contribution of
supplemented domestic rabbits, whose guard hairs could be distinguished from hairs of wild rabbits, to
the diet of the Iberian lynx. We also examined whether the consumption of domestic rabbits varied with
the availability of wild rabbits, and with the duration of exposure to supplemental food. Domestic rabbits
made up over 50% of the diet. Consumption of domestic rabbits decreased non-linearly as the relative
abundance of wild rabbits increased; however, this pattern was true only above a threshold density of
one wild rabbit km1. Below this threshold, supplementation was apparently strictly necessary to retain
Iberian lynx. The consumption of domestic rabbits did not increase with the length of the supplementation
period. Lynx continued consuming wild rabbits proportionally to their abundance, suggesting lynx
did not become dependent upon supplemental food. Understanding how the abundance of natural food
modulates consumption of supplemental food may help to adjust supplementation schedules to food
availability and to the needs of the target populations